A foot pedal, which swings a waste flap from a closed position to an opened position, is disposed near a section on a floor of an aircraft lavatory unit directly below a waste compartment. A foot pedal support mechanism is configured such that the foot pedal at the upper limit position is inclined and supported with a foot pedal rear end located directly below the waste compartment being located above a foot pedal front end away from the waste compartment and that the foot pedal rear end swings in a vertical direction by using the foot pedal front end as a fulcrum.